Standstill-positioning and restarting arrangement for a linear induction motor driven vehicle

ABSTRACT

An arrangement permitting standstill-positioning and subsequent restarting of a vehicle running on a track under the action of a linear induction motor. The track and the support members on the vehicle have cooperating projections and recesses which coincide at predetermined stop-and-go points of the track to mechanically catch the vehicle and to increase the restarting force by reducing the distance between the magnetic field and armature structures of the motor.

United States Patent 1 1 1111 3,736,881

Lorinet 5] June 5, 1973 541 STANDSTILL-POSITIONING AND 3,641,939 2/1972Remy ..104 14s LM RESTARTING ARRANGEMENT FOR A 3,697,838 1972 New..3l8/135 LINEAR INDUCTION MOTOR DRIVEN VEHICLE [75] Inventor: Jean-PaulPhilippe Lorinet, Greno- P'imaTyEmmi'1eT-Gera|d Fol'lenla ble, FranceAssistqnt Examiner(i orge H. Lihman [73] Assignee: Merlin Gel-in,Societe Anonyme, i gg iz g stlevens Davldson Mlner Grenoble, France Swen0S er [22] Filed: Feb. 8, 1972 [57] ABSTRACT 21 A LN .:224,540 l 1 pp 0An arrangement permrttmg standstlll-posltionmg and subsequent restartingof a vehicle running on a track Forelg" Application Priority Data underthe action of a linear induction motor. The

Feb. 11,1971 France ..71047o4 track and the pp members on the vehiclehave cooperating projections and recesses which coincide [52] U.S. Cl..104/148 LM, 310/12, 318/135 at predetermined stop-and-go points of thetrack to [51] IIILCL ..B| 13/00, H02k41/O2 mechanically catch thevehicle and to increase the [58] Field of Search ..104/148 LM, 148 MS,restarting force by reducing the distance between the 104/148 SS; 214/38BB; 310/12, 13; 318/ magnetic field and armature structures of themotor.

[56] References Cited 18 Claims, 10 Drawing Figures UNITED STATESPATENTS R12,620 3/1907 Slick.'. ..2l4/38 BB 422 /24 /38 46 2 50 i0 1 I JU 2/ 1 1 A B 20 E i] [1 L] STANDSTILL-POSITIONING AND RESTARTINGARRANGEMENT FOR A LINEAR INDUCTION.

MOTOR DRIVEN VEHICLE This invention relates to a standstill-positioningand restarting arrangement for a vehicle driven by a linear inductionmotor along a predetermined path.

Generally, the linear induction motor has an armature structure and amagnetic field structure, one of which is carried by the vehicle, theother extending along the path. For instance, the vehicle may carry anarmature plate which co-operates with confronting portions of the polefaces of a plurality of distinct magnetic field units, or stators,regularly spaced apart along the path. Confronting portions of thearmature and of the magnetic field structure define an air gaptherebetween and the magnetic field structure, when polyphase energized,produces a magnetic field traveling longitudinally through the air gapto drive the armature. It has already been suggested to modulate thethrust produced by the traveling field (and, of course, the magnitude ofthe magnetic field itself) by varying the width of the air gap along thepath of displacement of the vehicle.

It is a first object of the invention to provide a simple and reliablearrangement permitting to catch and position the vehicle in a stable wayat predetermined locations (hereinafter to be called stop-and-go points)of the path.

It is a further object of the invention to provide a simple positioningarrangement providing increased restarting force of the motor to permitthe vehicle to restart automatically after having been arrested at saidstop-and-go points.

It is a further object of the invention to provide a simplestandstill-positioning and restarting. arrangement for a conveyancedevice comprising one or more vehicles to be moved on a surface coveredby a gridwork of tracks or guide ways and to be arrested atpredetermined intersections of said tracks or guide ways.

In the arrangement according to the invention the guide means guiding avehicle along the path are adapted to mechanically catch the vehicle atthe stopand-go points and to reduce concurrently the width of the airgapby engagement of a number of projections into corresponding coincidentrecesses of the guide means.

The force for the holding of the interlock of the projections andrecesses in position can result from the weight of the moving load orfrom any suitable elastic system. The positioning may result fromvariations in the shape of the guide way of the vehicle, for instancethrough cup-shaped depressions into which the support members of themovable load, for instance rollershaped members, penetrate partially andfit. In the case of a load comprising two or more shafts, each equippedwith a pair of rollers, means are provided which permit the smoothpassage of the rollers outside of the stopandgo locations.

The positioning system in accordance with the invention makes itpossible to define precisely a stable equi librium which lends itselfalso to a change of tracks in a particularly simple fashion. For thispurpose, the moving vehicle or load may be equipped with a second seriesof support members capable of cooperating with at least one second trackwhich crosses the first and the point of intersection of which with thelatter also corresponds to a stable positioning location. Under theaction of the linear motor, the load, brought into said position andheld in said position by the catching mechanism in accordance with theinvention after deenergization or neutralization of the motor associatedwith the first track, can be switched onto the second track byenergizing the suitable motor associated with said second track.

The arrangement in accordance with the present invention also makespossible a step-by-step displacement by deenergizing or cancelling outthe driving thrust of the propulsion motor immediately before or at thetime of the locking engagement of the load in the next standstillposition. The decrease in thickness of the gap which results from thepositioning makes it possible to release the load by a new excitation ofthe motor the force of which is then sufficient to cause the emergenceof the rollers from the positioning cup.

In the case of a linear motor applied to the propulsion of a vehicle orof a freight carriage, the magnetic field structure may be connected tothe moving vehicle and cooperate with plate-shaped armatures extendingalong the path of displacement or, conversely, the magnetic field unitsmay be staggered as stators along said path, each vehicle bearing thenan armature plate confronting the pole surfaces of the stators. Thesupport membersof the moving part of the conveyance device can be ofdifferent types, for instance having rollers running on stationwayrunners or areas, or of the runner type running on members-mounted forrotation around stationary shafts and staggered or arranged in space soas to define travel bands along the guide way or track. The arrangementof the positioning device in accordance with the invention is, ofcourse, a function of the structural characteristics of the supportingandguiding device, and numerous variants can be contemplated.

The arrangement in accordance with the invention lends itselfparticularly well to a system for the handling and distribution of loadshaving a gridwork of displacement tracks arranged in intersectingcolumns and lines, as in checkerboards. They have already been proposedhandling devices of this kind for the propulsion of loads by means oflinear induction motors the stator elements of which are arranged alonghandling tracks, each load bearing an armature plate subjected to theaction of the confronting stator elements. In the known arrangements,the loads or carriages are equipped with skates or rubbing surfaceswhich rest on travel tracks composed of balls or pivoting rollers. Theuse of balls or pivoting rollers is in particular necessary in theintersection zones of changes of direction of two tracks in which a loadwhich has stopped in a given position can be displaced at right anglesto the prior displacement along a perpendicular branch track. Thepositioning of the load in a switching zone is effected by subdivisionof the active stator element into two parts and by feeding of the latterin such a manner as to produce opposite forces of displacement of theload the centering of which takes place after successive oscillations ofdecreasing amplitudes. The present invention makes it possible toimprove and accelerate the positioning at a precise point by adding tothe positioning by opposing thrust a mechanical releasable lockingengagement.

The known support balls of the load are fragile and of unreliableoperation, their resistance to rolling varying in particular with theirdegree of dirtying. In accordance with one development of the presentinvention,

the travel tracks consist of rollers mounted for rotation on stationaryshafts extending perpendicular to the general direction of the track soas to permit easy rolling on the load on said roller track. The zones ofintersection of the tracks are equipped with crossing rollerways andcorrespond to positioning locations of each track in such a manner thata carriage moving on one of the tracks is caused to stop at a centralposition adapted to enable it to move subsequently along any of theswitching tracks or directions selected. The relative positioning of therollers is, of course, so adapted as to permit the passage of thecarriage after the lifting phase corresponding to the departure from thestillstand position.

The use of rollers with fixed shafts facilitates the guiding of themoving loads or vehicles and permits a rapid damping of the oscillationsaround the stillstand position constituting a position of stableequilibrium. For this purpose, the rollers are advantageously mountedelastically so as to slide axially when they come into contact with arunner of the load which becomes locked in the stillstand position. Theelastic mounting also facilitates the separation of the moving load fromthe rolling members of the non-selected track, this separation takingplace positively during a movement of translation having a componentperpendicular to the orientation of the rollers of the nonselectedtrack. This displacement is compensated for by a slight sliding of therollers along their shaft until the removal and freeing of the rollerswhich automatically return into their position of equilibrium under theaction of the elastic forces acting on them.

In the case of an armature of ferromagnetic material, an intense forceof attraction acts between the magnetic field structure and the armaturestructure tending to cause the latter to stick to each other. This forceincreases greatly as a function of the decrease in the spacing ordistance present between the two structures, and it is easy tounderstand that in a stillstand position with decreased air gap it iscapable of assuming high values which effectively lock the moving in thestillstand position. This large force adds to that corresponding to theweight of the vehicle and must be overcome by the thrust of the linearmotor for a releasing of the moving load. It is possible to overcomethis additional attraction partially by utilizing an armature element ofa non-ferromagnetic conductive material, such as copper or aluminum.This matter solution seems preferable in ordinary handling installationsin which the locking force should preferably depend only slightly on thewidth of the airgap between the armature and magnetic field structures.

Other advantages and characteristics of the invention will becomeevident from the following description of several embodiments of theinvention, given by way of illustration only and which have been shownin the accompanying drawings in which FIG. 1 is a schematic plan view ofa conveyance device equipped with a positioning device in accordancewith the invention;

FIG. 2 is a side view on a larger scale of the installation shown inFIG. 1;

FIG. 3 is a view similar to that of FIG. 1, showing a variant of theinvention comprising stationary roller members defining a displacementtrack;

FIG. 4 is a side view similar to that of FIG. 2 of the installationshown in FIG. 3;

FIG. 5 is an elevation on a larger scale of the installation shown inFIG. 3;

FIG. 6 is a view similar to that of FIG. 5, showing another variant ofthe invention with a movable load equipped with rollers;

FIG. 7 is a schematic plan view of parts of a handling installation ofthe checkerboard type comprising intersecting load rolling tracksequipped with positioning devices in accordance with the invention;

FIG. 8 is a schematic view in perspective of a positioning zone of theinstallation of FIG. 7, only the lower part of the support of the loadbeing shown;

FIG. 9 is a detail view of FIG. 8, showing a possible mounting of aroller member;

FIG. 10 is a schematic view illustrating the relative position of therollers of a rolling track according to FIG. 7, permitting step-by-stepdisplacement with a lowering of the change only in the standstillpoints; in this figure various successive positions assumed by the loadduring its displacement have been shown.

In FIGS. 1 and 2 a linear induction motor comprises a magnetic fieldstructure composed of stator elements 10, 12 staggered along a path ofdisplacement of an armature element 14 capable of moving in thedirection of traveling of the magnetic field produced by the polyphaseenergizable elements 10, 12. The armature element is connected to amovable load schematically represented by a vehicle or carriage 16 theframe of which is equipped with two spaced axles 18, 20, each of whichbears a pair of support rollers 22, 22, 24, 24. The rollers 22, 22', 24,24' are adapted to roll on rails 26, 28 which constitute a trackextending in the said direction of displacement and guiding the movingload in such a manner as to maintain a substantially constant distanceor gap between the plate-shaped armature element 14 and the airgap orpole surface of the stator elements 10, 12 which extend along the track.Such arrangements are well known and it is obvious that this example ofhandling installation has been selected only to facilitate anunderstanding of the description which follows. The armature plate 14can actuate any mobile.

The rollers 22, 24 and 22, 24' are disaligned with respect to each otherso as to cooperate with different travel paths or raceways of the rails26, 28 respectively, shown in FIG. 1 at 30, 32 and 34, 36. The track 26,28 has two positioning locations or stop-and-go points A, Bcorresponding to zones of stopping of the vehicle 16, in which the paths30 to 36 are provided with notches or recesses 38, 40, 42, 44 adapted toreceive the rollers 22, 22' and 46, 48, 50, 52 arranged opposite therollers 24, 24' capable of engaging therein. The distance between thenotches 38, 40 and 46, 48 corresponds, of course, to the distancebetween the axles of the rollers 22, 24, 22, 24. During the displacementof the carriage 16 along the track 26, 28, the rollers 22 to 24' embedthemselves in the corresponding notches in the positions A and B so asto define the positioning locations of stable equilibrium in which thecarriage 26 is held by its own weight. The penetration of the rollers 22and 24 in the notches of the rails is accompanied by a slight loweringmovement which decreases the spacing or airgap between the armature 14and the facing stator surface 10 or 12. The decrease in the gap of thelinear motor is accompanied in a known manner by an increase in theforce of propulsion which is beneficial for permitting the releasing bylifting of the rollers 22 to 24' from the notches. The stators 10 or 12must,

of course, be deenergized at the proper moment upon the arrival of thecarriage l6, detected in any manner to permit the stopping of the latterin position A or B. It is also possible to divide the stator in thepositioning zone into two active elements acting in opposite directionswhich urge the carriage towards a central equilibrium positioncorresponding to the stillstand position defined by the notches providedin the rails. In such a variant the positioning of the carriage 16 isfully assured, any excess movement being accompanied by an increasedcentering effort which brings the vehicle back towards the centralposition where it rests after a number of oscillations.

The invention also applies to installations in which the magnetic fieldstructure of the linear motor is carried by the carriages 16, thearmature elements being then in the form of stationary plates arrangedalong or constituting the rolling and guiding track of the carriages 16.This type of installation is more particularly suitable for tracks ofvery great length which would otherwise require costly wound statorelements. The decrease in the gap of the motor at the standstill pointsis obviously retained in full in this type of installation.

The nature of the guide and support elements of the carriages 16 may bedifferent, and FIGS. 3 to 5 show a variant embodiment of the inventionin which the load 16 is equipped with a pair of elongated lateralrunners 56, 58 capable of sliding on travel paths formed of rollers 60,62 extending along the entire length of the path of the carriage andwhich are mounted for rotation on fixed horizontal shafts extendingperpendicular to the path. Positioning recesses or cups 64, 66 and 68,70 are provided in runners 56 and 58, respectively, and longitudinallyspaced so as to coincide with the rollers 60 and 62 at the standstill orstop-and-go points, such as C, D, where a pair of rollers 60 is receivedby the recesses 64, 68 and another pair of rollers 62 by the recesses66, 70 to position the carriage 16. On the path intermediate the pointsC and D a sufficient number of support rollers permits the passage ofthe recesses 64 to 70 without possibility of engagement of the latter onone of the rollers. This may be obtained by disposing, as shown, pairsof rollers 60 and 62 on the same transverse axis. The operation of thisinstallation is, of course, analogous to that of the embodiment of FIGS.1 and 2, only the respective position of the support and guide membersbeing different.

In the example shown in FIGS. 1 and 2, each of the rollers 22, 22, 24,24 of a carriage 16 has its own displacement path so as to prevent thenotches 38 to 52 hindering or disturbing the passage of the otherrollers. FIG. 6 illustrates a variant embodiment of the inventionsimilar to that of FIGS. 1 and 2 but with a travel path in the form of asingle rail or area for all the rollers secured to the carriage 16. Thecarriage 16 is equipped with three axles 72, 74, 76, each bearing a pairof rollers, the intermediate axle 74 being closer to the axle 76 than tothe axle 76. In a stop-and-go position, shown in solid lines in FIG. 6,the track or rolling area 78 has transverse grooves or depressions 80,82, 84 of rounded shape the spacing of which corresponds to the distancebetween the axles 72, 74, 76, respectively, so as to permit anengagement of the rollers in coincident mating grooves and a locking bylowering of the carriage 16 in this position. It is seen that such alowering is possible only if all of the rollers of the axles 72, 74, 76are facing an associated groove and, by way of example, there has beenshown in dashed line the position of the carriage 16 at the time therollers of the axle 74 clear a groove 84. In this position anypositioning engagement is prevented, the carriage 16 being onlysupported by the end rollers 72 and 76. In this way one avoids jumpsupon passage over grooves when the carriage rolls beyond the positioninglocations. Of course, the position of the center of gravity of thecarriage should be taken into consideration, particularly upon thepassage of the end rollers, so as to avoid a possible tilting of thecarriage. Additional roller axles and grooves can be provided. FIG. 7shows by way of example an installation having fixed rollers capable ofcooperating with support runners carried by the moving load andcomprising two positioning locations or stopand-go points E, F providedin switching zones in which side tracks extend perpendicular to the maintrack. The main track is formed of two travel paths 86, 88, eachcomprising aligned rollers 90, 92 idly mounted on fixed horizontal axlesextending perpendicularly to the direction of the travel path, thespacing of the successive rollers in the zones of normal travel beingdetermined in such a manner as to assure at all points support of therunners coming into contact with them. At the positioning locations E, Feach travel path 86, 88 has three rollers 94, 96, 98 and 100, 102, 104,respectively, ar ranged in pairs and spaced in accordance with a givenpattern corresponding to that of the recesses provided in the runnerscarried by vehicle (not shown in FIG. 7). A positioning by mechanicalcatching is effected at least at any desired stopping point of the track86, 88 by an arrangement of the rollers identical to that of thelocation B. The positioning locations advantageously correspond toswitching zones where intersecting branch tracks extend perpendicularlyto the main track 86, 88. Each of these travel path tracks 106, 108 and110, 112 is preferably developed in a manner identical to that of thetrack 86, 88, the support rollers of the different tracks imbricating inthe crossing zones E and F. The carriage, not shown in FIG. 7, must, ofcourse, be equipped with pairs of runners capable of cooperating withthe perpendicular tracks. The arrangement of such a bifurcation orintersection will become more evident from the following description ofa variant embodiment shown in FIG. 8. The crossing points E, Fcorrespond to a positioning location for each of the correspondingtracks. The tracks 86, 88, 106, 108 and 110, 112 comprise a plurality offixed stator elements 114, 116 and 118 respectively aligned in thegeneral direction of the corresponding track. In a manner known per se,the position locations E and F comprise at least two stator elements ofeach of the tracks, said elements, which are arranged in a cross, beingcapable of being fed selectively so as to exert a thrust in onedirection or the other on the vehicle. Two elements of one and the sametrack may be energized in opposite directions to center the carriage insaid position of stop. The combined centering action by electromagneticforces and by mechanical catching forces makes it possible rapidly todampen the oscillations around the equilibrium position and to maintainthe movable load in the stillstand position even after elimination ofthe electromagnetic force, that is to say, the deenergization of thestator elements.

The selection of the track of travel is effected by excitation of aseries of corresponding stator elements, said excitation producing amovement in the selected direction which causes a lifting and adisengagement of the vehicle. Such a lifting makes it possible toseparate the runner from the travel rollers of the track which has notbeen selected.

The positioning and transfer device in accordance with the invention maybe applied to a handling system comprising a gridwork of rows andcolumns of load travel tracks known as checkerboard handling system.FIG; 8 shows by way of example in perspective a positioning locationcorresponding to the crossing of a row and a column of travel tracks ofsuch a checkerboard. The carriage or supports of the loads,schematically represented by the flat surface 120, are equipped withfour pairs of runners, two of which pairs 122, 122' and 124, 124' extendin the direction of displacement indicated by the arrow X in FIG. 8,while two other pairs thereof, 126, 126' and 128, 128' extend in adirection at right angles indicated by the arrow Y. The runners 122 to128' laterally surround the frame 120 and the armature (not shown)carried by the vehicle in substantially rectangular or square shape. Atravel track extending in the direction of the arrow X is formed of twoseries of rollers 130, 132 idly mounted on horizontal axles extendingparallel to the direction Y. The transverse distance between the seriesof rollers 130, 132 corresponds to the distance between the runners 122,122, 124, 124' in such a manner that the vehicle 120 is capable ofsliding along said track X while being supported by the runners rollingon the rollers 130, 132. In a similar manner, two series of alignedrollers 134, 136 extend parallel to the direction indicated by the arrowY to form a second travel track on which the runners 126, 126', 128,128' are capable of rolling for displacement of the movable load 120 ina direction along the arrow Y. Each runner 122 to 128' has a cupshapeddepression 138 in which there can house itself a circumferential portionof a roller of one of the travel tracks in engaged or lowered positionof the frame 120. The length of each runner 122 to 128' is, of course,adapted to the longitudinal spacing of the respective support rollers130 to 136 and the ends are carried upward to improve the smooth passageof the runners on the rollers. The assembly is arranged in such a mannerthat each runner rests on at least two rollers in any intermediateposition between two positioning locations and it is easy to understandthat under these conditions the load is at all time supported at atleast four points avoiding any lowering engagement of runners on anyroller in all intermediate positions. In the positioning location,however, each runner is supported by a single roller which coincideswith the corresponding cup which fits therein. FIG. 10 schematicallyillustrates the relative positioning, for instance of the runners 122,124' which cooperate with the rollers 132, for different positions ofthe frame or carriage 120 moving in the direction of the arrow X. Therollers in engagement are indicated in the figure by solid circles,while the free rollers are indicated by empty circles. The letter Lindicates on FIG. 10 the minimum length of the carriage 120, the letterG indicating the zone in which the center of gravity of the moving load120 must be located. The distance between two positioning or stop-and-golocations is indicated by the letter P which corresponds to the pitch ofthe lines or columns of the checkerboard. The size of the boxes of thecheckerboard is indicated at P.

It is needless to describe in detail the different phase of displacementillustrated in FIG. 10 and it will be merely pointed out that the phaseillustrated in the first line and the last line correspond topositioning locations, the movable load having been transferred towardsthe following column. The frame of the movable load comprises across-shaped armature schematically indicated in dashed line 140 in FIG.8, capable of cooperating with stator elements which are not shown butare similar to those in FIG. 7. The arrangement of the rollers and ofthe associated runners 122, 124 is obviously symmetrical to thepreviously described arrangement of the rollers 132 and the associatedrunners 122' and 124'. The same arrangement is employed again for therollers 134 and 136 as well as the associated runners 126, 126, 128, 128of the track extending in the direction indicated by the arrow Y.

The functioning of the arrangement illustrated in FIGS. 8 and 10 isevident from the description previously given. A carriage 120 moving inthe direction indicated by the arrow X under the action of the linearmotor, and more particularly of the stators arranged parallel to saiddirection, is supported by the runner 122 and 124' traveling on thetravel paths formed of the rollers 130 and 132 respectively. At themoment when the movable load reaches the position shown in FIG. 8, therecesses or cups 138 of the runners 122 to 124 fit on the correspondingsupport rollers 130, 132 which alone are facing the runners 122 to 124'.The movement of the engagement of the runners is accompanied by alowering or descent of the frame 120 and therefore a movement of thearmature towards the pole surface of the stators, one of which isenergized from this moment on, in opposite direction so as to urge in aknown manner the frame 120 towards the centering position illustrated inFIG. 8. In case of overshoot, the action of the stator acting inopposite direction tends automatically to return the movable loadtowards the engagement position. It should be noted that the cups 138 ofthe runners 126, 126 and 128, 128' corresponding to the orthogonaldirection of displacement Y also come into the position shown in FIG. 8opposite a support roller which is alone facing the said runners. Thelowering movement due to the engagement of the runners 122 to 124' istherefore permitted by engagement of the recesses of the runners 126 to128' with rollers 134, 136 of the perpendicular track. Starting from thestillstand position indicated in FIG. 8, the movable load 120 can bedisplaced either in the direction X by exciting the stator elementsoriented in said direction or in the direction Y by exciting the statorelements associated with this direction of travel. The small gap presentbetween the armature 140 and the excited stator elements makes itpossible to have a substantial thrust capable of disengaging the cups138 from the support rollers. In case of a displacement in the directionindicated by the arrow X, the rollers which come into contact with theinclined surfaces of the cups 138 cause a lifting of the runners 122 to124' and therefore a lifting of the frame 120 and of the associatedrunners 126 and 128. This lifting makes it possible to remove theselast-mentioned runners away from their support rollers, avoiding anysliding or rubbing which might substantially increase the resistance toadvance. For this purpose it is advantageous to round the travel surfaceof the rollers so as to facilitate the separation of the runners fromsaid surfaces. In similar manner, displacement along the direction Ycauses a lifting of the frame 120 by the action of the rollers 134, 136on the marginal curved portions of the cups 138 of the runners 126 to128', which lifting moves the inactive runners 122 to 124 away fromtheir support rollers 130, 132. The change in path or direction oftravel of the movable load 120 therefore takes place automatically bysimple selection of the excited stator without requiring any change inthe support or guiding members.

FIG. 9 shows a variant embodiment of the invention which makes itpossible to reduce the frictional forces exerted by the positioningrollers in the case of displacement along a perpendicular direction. Thebushing 144 of the roller 142 is mounted for rotation and sliding on afixed axle 146. The roller 142 is surrounded by elastic stops consistingof fixed housings 143, 143' integral with the axle 146 and one of theends 145, 145 of which adjacent the hub of the roller 142 is mountedmovable while being urged in the direction of the roller 142 bycompression springs 148, 150 interposed between the ends 145, 145 andthe housing 143, 143. The relative displacement of the ends 145, 145 islimited in the direction of the roller 142 by collars of the fixedhousing 143, 143. It is easy to see that a runner, schematically shownat 122, which moves in the direction of the arrow X and comes intocontact with the surface of the positioning roller 142 is capable ofdriving the latter axially during the engagement phase in opposition tothe action of the spring 148. The lateral displacement of the roller 142avoids any friction between the runner and the roller 142 whilepermitting return to the initial position of the roller 142 upon therelease of the latter by a lifting of the runner due to thedisengagement of the movable load from the rest position. Thearrangement is, of course, bi-directional. Any other suitable system,for instance a slight relative pivoting of the roller permitted by acertain flexibility, makes it also possible to obtain the desiredresult.

The interlocking or catching force depends on the profile of themarginal edges of the depressions or recesses 138 and the slopes will beof greater or lesser steepness, depending on the effect desired.

The invention is, of course, in no way limited to the embodiments whichhave been more particularly described and shown in the accompanyingdrawings but it rather extends to any variant remaining within the scopeof mechanical or electrical equivalents, and particularly to the variantin which the stator structure or the linear motor is borne by themovable load, the armature structure being stationary to extend alongthe travel tracks. Any of the support and guide arrangements describedwith reference to FIGS. 1 to 7 can obviously be utilized in a handlingsystem of the checkerboard type more particularly described withreference to FIGS. 8 to 10.

What is claimed is l. A standstill-positioning and restartingarrangement for a vehicle having support members running on a linearlyextending track under the action of a linear induction motor deviceincluding a magnetic field structure cooperating with an armaturestructure, one of said structures being movable with said vehicle, theother structure extending along said track so that the value of thedriving force exerted by said linear induction motor device on saidvehicle is governed by the distance between confronting air gap faces ofsaid structures, respectively, said support members and said track beingadapted to mechanically catch and position said vehicle and to reducesaid distance at predetermined stop-and-go points of said track.

2. A conveyance device to propel a vehicle along a predetermined pathand to arrest and restart the vehicle at predetermined stop-and gopoints of the path, comprising support and guide means to support andguide said vehicle along said path;

a linear induction motor device having a magnetic field structure and anarmature structure, one of said structures being movable with saidvehicle, the other structure being stationary and extending along saidpath, said structures defining cooperating airgap faces extendingparallelly to the longitudinal direction of said path so that the airgapface of said one structure passes over the air gap face of said otherstructure during the movement of said vehicle along said path under theaction of a traveling magnetic field produced by said magnetic fieldstructure, when energized;

said support and guide means being adapted to reduce the distanceseparating confronting portions of the air gap faces of said structuresat said stopand-go points pursuant to the releasable catching ofcoincident interfitting projections and recesses of said support andguide means.

3. A conveyance device comprising a vehicle,

a linearly extending track for said vehicle,

support members on said vehicle adapted to run on said track,

a linear induction motor device having a magnetic field structure and anarmature structure, one of said structures being movable with saidvehicle, the other structure extending along said track,

said other structure defining aligned air gap faces extending parallellyto said track, said one structure defining a cooperating air gap faceadapted to pass over said aligned air gap faces parallelly thereto andclosely spaced therefrom to drive said vehicle along said track underthe action of a magnetic field traveling between confronting portions ofsaid air gap faces of said structures upon energizing of said magneticfield structure,

said support members and said track comprising a plurality of rollermeans spaced apart in the direction of said track and in rollingengagement with runner means longitudinally extending in the directionof said track,

said runner means comprising a plurality of longitudinally spaced apartrecesses, shaped to accommodate a circumferential portion of said rollermeans,

said roller means and said recesses of said runner means beingpositioned to catch said vehicle at predetermined stop-and-go points ofsaid track by interfitting of coinciding roller means and recessesthereby diminishing at said stop-and-go points the spacing of the airgap faces of said structures so as to increase the starting forceexerted on said vehicle by said magnetic field permitting said rollermeans to leave said recesses upon energizing of said magnetic fieldstructure.

4. A conveyance device as set forth in claim 3, said magnetic fieldstructure being carried by said vehicle,

said armature structure comprising stationary armature plates arrangedalong said track.

5. A conveyance device as set forth in claim 3, said armature structurebeing carried by said vehicle, said magnetic field structure comprisingmagnetic field units regularly spaced apart along said track.

6. A conveyance device as set forth in claim 5, said armature structurebeing substantially only composed of electrically conductive andnon-magnetizable material to diminish the attraction forces actingbetween the air gap faces of said structures.

7. A conveyance device as set forth in claim 3, said runner means beingstationary and extending along the entire length of said track, saidroller means being carried by said vehicle.

8. A conveyance device as set forth in claim 7, said runner meanscomprising a pair of parallel guide rails cooperating with two pairs ofrollers having different track gages, said rails comprising for saidpairs of rollers different running surfaces having notches to accomodatethe corresponding rollers, at each stop-and go point.

9. A conveyance device as set forth in claim 7, said runner meanscomprising a generally flat single running area having a plurality ofnon-equidistant transversely extending grooves at each stop-and-go pointto accomodate a corresponding number of mating roller means carried bysaid vehicle.

10. A conveyance device as set forth in claim 3, said runner means beingcarried by said vehicle to run on aligned idle rollers spaced apartalong the entire length of said track.

11. A conveyance device as set forth in claim 10, said runner meanscomprising at least a pair of runners longitudinally extending alongsaid vehicle laterally of said one structure, each runner running on aset of rollers spaced apart along said track in such a manner that therunner engages always at least two rollers and that the recesses of therunner coincide with a corresponding number of rollers only at saidstop-and-go points.

12. A conveyance device comprising 2 a vehicle,

two coplanar sets of parallel tracks for said vehicle to form a gridworkof crossing tracks,

a first set of support members on said vehicle adapted to run on thetracks of one set,

a second set of support members on said vehicle adapted to run on thetracks of the other set,

a linear induction motor system having a composite selectivelyenergizable magnetic field structure and an armature structure, one ofsaid structures being movable with said vehicle, the other structurebeing coextensive with said gridwork,

said other structure defining a plurality of substantially coplanar airgap faces, said one structure defining a cooperating air gap faceadapted to pass over said coplanar air gap faces closely spacedtherefrom to drive said vehicle along selected tracks according toselective energizing of said magnetic field structure,

said first and said second set of support members being disposedperipherally of said one structure,

said support members and portions of said tracks at predeterminedintersections thereof comprising coinciding interfitting projections andrecesses to mechanically catch said vehicle at said intersections and toreduce the distance between the air gap faces of said structures.

13. A conveyance device as set forth in claim 12, said support memberscomprising at least two pairs of recessed runners, said trackscomprising pairs of rollers the spacings of which in the direction ofthe corresponding tracks coinciding only at said predeterminedintersections with the spacings of the recesses of said runners.

14. A conveyance device as set forth in claim 13, said rollers beingshaped to enhance the disengagement of the support members from therollers associated with the non-selected direction of displacement uponrestarting of the vehicle.

15. A conveyance device as set forth in claim 13, said rollers beingsupported for resilient lateral movement.

16. A conveyance device comprising a vehicle,

a stationary guide way for said vehicle,

support members on said vehicle running on said guide way,

a linear induction motor to drive said vehicle along said guide way andincluding a magnetic field structure and an armature structure, one ofsaid structures being movable with said vehicle, the other structureextending along said guide way,

said guide way comprising at predetermined points surface inequalitiesshaped and positioned to accomodate peripheral mating parts of saidsupport members of said vehicle to position said vehicle at said pointsunder the action of the weight of said vehicle and to reduce thedistance between said structures thereby to increase the restartingforce exerted by said motor on said vehicle upon energizing of saidmagnetic field structure in order to per mit the vehicle to lift and todisengage said surface inequalities.

17. A conveyance device for driving a vehicle along a predeterminedpath, comprising a linear induction motor to drive said vehicle alongsaid path and including a magnetic field structure and an armaturestructure, one of said structures being movable with said vehicle, theother structure extending along said path,

guide means to guide said vehicle and said one structure along saidpath,

said guide means being adapted to impart to said one structure atpredetermined points of said path sudden movements transverse of saidpath to locally reduce the distance separating said one structure fromsaid other structure thereby to position said vehicle at standstill atsaid points upon deenergizing of said magnetic field structure and topermit restarting of said vehicle upon re-energizing of said magneticfield structure.

18. A conveyance device comprising a vehicle,

a pair of tracks for said vehicle, crossing at an angle,

first support members on said vehicle adapted to run on one of saidtracks,

second support members on said vehicle adapted to run on the other ofsaid tracks,

said first and second support members extending on said vehicle ingeneral directions crossing at an angle corresponding to said crossingangle of said tracks,

of said tracks at the intersections thereof comprising coincident matingprojections and recesses engaging each other to catch said vehicle atsaid intersection and to reduce the distance between said structures atsaid intersection.

1. A standstill-positioning and restarting arrangement for a vehiclehaving support members running on a linearly extending track under theaction of a linear induction motor device including a magnetic fieldstructure cooperating with an armature structure, one of said structuresbeing movable with said vehicle, the other structure extending alongsaid track so that the value of the driving force exerted by said linearinduction motor device on said vehicle is governed by the distancebetween confronting air gap faces of said structures, respectively, saidsupport members and said track being adapted to mechanically catch andposition said vehicle and to reduce said distance at predeterminedstop-and-go points of said track.
 2. A conveyance device to propel avehicle along a predetermined path and to arrest and restart the vehicleat predetermined stop-and-go points of the path, comprising : supportand guide means to support and guide said vehicle along said path; alinear induction motor device having a magnetic field structure and anarmature structure, one of said structures being movable with saidvehicle, the other structure being stationary and extending along saidpath, said structures defining cooperating airgap faces extendingparallelly to the longitudinal direction of said path so that the airgapface of said one structure passes over the air gap face of said otherstructure during the movement of said vehicle along said path under theaction of a traveling magnetic field produced by said magnetic fieldstructure, when energized; said support and guide means being adapted toreduce the distance separating confronting portions of the air gap facesof said structures at said stop-and-go points pursuant to the releasablecatching of coincident interfitting projections and recesses of saidsupport and guide means.
 3. A conveyance device comprising : a vehicle,a linearly extending track for said vehicle, support members on saidvehicle adapted to run on said track, a linear induction motor devicehaving a magnetic field structure and an armature structure, one of saidstructures being movable with said vehicle, the other structureextending along said track, said other structure defining aligned airgap faces extending parallelly to said track, said one structuredefining a cooperating air gap face adapted to pass over said alignedair gap faces parallelly thereto and closely spaced therefrom to drivesaid vehicle along said track under the action of a magnetic fieldtraveling between confronting portions of said air gap faces of saidstructures upon energizing of said magnetic field structure, saidsupport members and said track comprising a plurality of roller meansspaced apart in the direction of said track and in rolling engagementwith runner means longitudinally extending in the direction of saidtrack, said runner means comprising a plurality of longitudinally spacedapart recesses, shaped to accommodate a circumferential portion of saidroller means, said roller means and said recesses of said runner meansbeing positioned to catch said vehicle at predetermined stop-and-gopoints of said track by interfitting of coinciding roller means andrecesses thereby diminishing at said stop-and-go points the spacing ofthe air gap faces of said structures so as to increase the startingforce exerted on said vehicle by said magnetic field permitting saIdroller means to leave said recesses upon energizing of said magneticfield structure.
 4. A conveyance device as set forth in claim 3, saidmagnetic field structure being carried by said vehicle, said armaturestructure comprising stationary armature plates arranged along saidtrack.
 5. A conveyance device as set forth in claim 3, said armaturestructure being carried by said vehicle, said magnetic field structurecomprising magnetic field units regularly spaced apart along said track.6. A conveyance device as set forth in claim 5, said armature structurebeing substantially only composed of electrically conductive andnon-magnetizable material to diminish the attraction forces actingbetween the air gap faces of said structures.
 7. A conveyance device asset forth in claim 3, said runner means being stationary and extendingalong the entire length of said track, said roller means being carriedby said vehicle.
 8. A conveyance device as set forth in claim 7, saidrunner means comprising a pair of parallel guide rails cooperating withtwo pairs of rollers having different track gages, said rails comprisingfor said pairs of rollers different running surfaces having notches toaccomodate the corresponding rollers, at each stop-and-go point.
 9. Aconveyance device as set forth in claim 7, said runner means comprisinga generally flat single running area having a plurality ofnon-equidistant transversely extending grooves at each stop-and-go pointto accomodate a corresponding number of mating roller means carried bysaid vehicle.
 10. A conveyance device as set forth in claim 3, saidrunner means being carried by said vehicle to run on aligned idlerollers spaced apart along the entire length of said track.
 11. Aconveyance device as set forth in claim 10, said runner means comprisingat least a pair of runners longitudinally extending along said vehiclelaterally of said one structure, each runner running on a set of rollersspaced apart along said track in such a manner that the runner engagesalways at least two rollers and that the recesses of the runner coincidewith a corresponding number of rollers only at said stop-and-go points.12. A conveyance device comprising : a vehicle, two coplanar sets ofparallel tracks for said vehicle to form a gridwork of crossing tracks,a first set of support members on said vehicle adapted to run on thetracks of one set, a second set of support members on said vehicleadapted to run on the tracks of the other set, a linear induction motorsystem having a composite selectively energizable magnetic fieldstructure and an armature structure, one of said structures beingmovable with said vehicle, the other structure being coextensive withsaid gridwork, said other structure defining a plurality ofsubstantially coplanar air gap faces, said one structure defining acooperating air gap face adapted to pass over said coplanar air gapfaces closely spaced therefrom to drive said vehicle along selectedtracks according to selective energizing of said magnetic fieldstructure, said first and said second set of support members beingdisposed peripherally of said one structure, said support members andportions of said tracks at predetermined intersections thereofcomprising coinciding interfitting projections and recesses tomechanically catch said vehicle at said intersections and to reduce thedistance between the air gap faces of said structures.
 13. A conveyancedevice as set forth in claim 12, said support members comprising atleast two pairs of recessed runners, said tracks comprising pairs ofrollers the spacings of which in the direction of the correspondingtracks coinciding only at said predetermined intersections with thespacings of the recesses of said runners.
 14. A conveyance device as setforth in claim 13, said rollers being shaped to enhance thedisengagement of the support members from the rollers associated withthe non-selected direction of displacement upon restarting of thevehicle.
 15. A conveyance device as set forth in claim 13, said rollersbeing supported for resilient lateral movement.
 16. A conveyance devicecomprising : a vehicle, a stationary guide way for said vehicle, supportmembers on said vehicle running on said guide way, a linear inductionmotor to drive said vehicle along said guide way and including amagnetic field structure and an armature structure, one of saidstructures being movable with said vehicle, the other structureextending along said guide way, said guide way comprising atpredetermined points surface inequalities shaped and positioned toaccomodate peripheral mating parts of said support members of saidvehicle to position said vehicle at said points under the action of theweight of said vehicle and to reduce the distance between saidstructures thereby to increase the restarting force exerted by saidmotor on said vehicle upon energizing of said magnetic field structurein order to permit the vehicle to lift and to disengage said surfaceinequalities.
 17. A conveyance device for driving a vehicle along apredetermined path, comprising : a linear induction motor to drive saidvehicle along said path and including a magnetic field structure and anarmature structure, one of said structures being movable with saidvehicle, the other structure extending along said path, guide means toguide said vehicle and said one structure along said path, said guidemeans being adapted to impart to said one structure at predeterminedpoints of said path sudden movements transverse of said path to locallyreduce the distance separating said one structure from said otherstructure thereby to position said vehicle at standstill at said pointsupon de-energizing of said magnetic field structure and to permitrestarting of said vehicle upon re-energizing of said magnetic fieldstructure.
 18. A conveyance device comprising : a vehicle, a pair oftracks for said vehicle, crossing at an angle, first support members onsaid vehicle adapted to run on one of said tracks, second supportmembers on said vehicle adapted to run on the other of said tracks, saidfirst and second support members extending on said vehicle in generaldirections crossing at an angle corresponding to said crossing angle ofsaid tracks, a linear induction motor system having a magnetic fieldstructure and an armature structure, one of said structures beingmovable with said vehicle, the other structure extending along bothtracks in a manner permitting to propel said vehicle along a selectedbranch track of said crossing tracks, said first and second supportmembers and portions of said tracks at the intersections thereofcomprising coincident mating projections and recesses engaging eachother to catch said vehicle at said intersection and to reduce thedistance between said structures at said intersection.